Materials Science Forum Vols. 809-810

Abstract: In order to prevent Zn₂SiO₄:Mn²⁺ with short decay time for 3D plasma display panels (PDPs) from the deterioration of the luminescence efficiency caused by vacuum ultraviolet (VUV) irradiation, MgF₂ coated Zn₂SiO₄:Mn²⁺ phosphor samples were prepared by a sol-gel process. The influence of the coating percentage on the photoluminescence properties was investigated.The results show that: MgF₂ coatings can improve the Zn₂SiO₄:Mn²⁺ phosphor emission intensity, brightness as well as VUV irradiation stability. And the optimal coating percentage on the luminescent intensity is also achieved: under 147 excitation, the optimal MgF₂ coating mass ratio is 0.8%, with the best brightness of 11.5% and improved VUV irradiation stability, compared with the raw phosphor.

Abstract: Self-assembled method for controllable fabrication of a hydrophobic triazine dithiol-silane composite film on 304 stainless steel (SS) is reported in this paper. Hierarchical structure composed of micro/nanofeatherlike surface was obtained by acid etching. After modification with 2-( Dibutylamino )-4,6-dimercapto-1,3,5-triazine ( DB ) and n-octadecyltrichlorosilane ( OTS ), the suface became hydrophobicity. By applying SEM, FTIR-RAS, and water contact angle analysis, the surface morphology and hydrophobicity of the as-prepared surfaces were studied in detailed. The results indicated that at the optimal condition, the surface showed a good hydrophobicity with a water contact angle as high as 152±3°. Possible growth mechanism of featherlike hierarchical structure was discussed. Additionally, the anticorrosion effect of the hydrophobic surface was studied by potentiodynamic polarization measurement. It showed that the surface covered with hydrophobic composite film was found to be more positive than bare and monolayer, the corrosion current was significantly lower to 1.68 nA/cm², and the corrosion potential shifted positively from-253 mV to-118 mV ( vs SEC ).

Abstract: The VN coatings were coated by chemical vapor deposition on T12 substrate using V₂O₅, H₂ and N₂ as reactants. Thermodynamic calculation and analysis of formation reaction of VN were done by thermodynamic potential function. As shown by the experimental results, chemical vapor deposition of the VN coating with preheating temperature of 973K and deposition temperature of 1573K under normal atmospheric pressure was feasible.

Abstract: An iron based composite coating reinforced by (Fe,Cr) ₇C₃ particles, with a thickness of 4.0 mm, was fabricated on the ductile cast iron substrate by means of a centrifugal casting and in situ techniques. The microstructure and properties of the composite coatings were investigated by optical microscope, X-ray diffraction, scanning electron micrograph, energy dispersive spectrum, microhardness tester and pin-on-disc wear tester. Results show that the composite coatings consists of primary (Fe,Cr) ₇C₃ carbides as the reinforcing phase and interdendritic (Fe,Cr) ₇C₃/γ eutectics accompanied by negligible graphite nodules as the matrix. The reinforcements are metallurgical bonded to the ductile cast iron substrate. Compared with unreinforced ductile cast iron, the composite coatings offer virtually a unique wear resistant behaviour under the condition of dry sliding with loads.

Abstract: Nitrogen-doped nanoTiO₂ sol was prepared by sol-gel method. The obtained sol was coated onto glass substrates by spin coating method, followed by drying at low temperature and calcined at high temperature. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible spectra (UV-Vis) . The XRD spectra showed that the crystal type of N-doped TiO₂ films was anatase. The SEM images showed that the surface of films were flat without obvious crack and average diameter was about 20 nm. The UV-Vis spectra showed that the absorbance of N-doped TiO₂ films at ultraviolet region increased. N-doping caused photocatalysis response wavelength to turn longer. The photocatalytic activity of N-doped TiO₂ films was researched through the degradation experiment of methyl orange under ultraviolet light. Higher photocatalytic degradation efficiency was exhibited compared to the pure TiO₂ films.

Abstract: The growth of microarc oxidation (MAO) coatings on aluminum substrates was controlled via changing solution temperature from 10 to 60 °C. The results show that an elevation of the temperature lowers the applied voltage and the coating thickness. The coating formed in low-temperature solution demonstrates large-sized pores and contains lots of elements only originating from solute such as P, W, and V. On the contrary, numerous small-sized pores disperse homogeneously on the coating synthesized in high-temperature solution. It is assumed that the variation of solution temperature affects the dissolving capacity of the alkaline solution and the adsorptive capacity of solute anions, thus dominating the growth behaviors of MAO coating.

Abstract: HfSiN/Cu/HfSiN/SiO₂/Si multilayer films were prepared on Si substrate via magnetron sputtering technology. Annealing experiments of samples among 400°C and 700°C were carried out in order to investigate the anti-diffusion performance of HfSiN thin film to Cu. XRD, AFM and FPP were used to characterize the structure, morphology and the resistivity of the thin films before and after annealing, respectively. The failure temperature and failure mechanism of HfSiN thin film were analyzed. The anti-diffusion failure temperature of HfSiN thin film is 600 °C. And the main reason is that a large number of Cu large particles passed through HfSiN diffusion barrier layer and reacted with Si substrate and oxygen to generate Cu₃Si and CuO with high resistance.

Abstract: In solar thermal storage system, the mixed chloride molten salt with the higher conversion efficiency than a single molten salt, but they are more corrosive than the often used nitride molten salts. In the presents work, aluminide and chromate coating were prepared on the surface of Inconel625 alloy by thermal packing method. The corrosion behaviors of thermal diffusion coating on the surface of Inconel625 alloy in mixed molten salts at 900°C were studied by using XRD and SEM equipped with EDS in the present work. The results showed that both of the two thermal diffusion coatings have sever corrosion in the mixed chloride molten salts, but thermal diffusion Al coating in the mixed chloride molten salt corrosion is more serious than thermal diffusion Cr coating, because Cr₂O₃ is more easily dissolved in the molten salt than Al₂O₃.

Abstract: Montmorillonite intercalated polyaniline material was prepared by Situ polymerization method,the effects ofinitiator content, polymerization time, temperature and other parameters on the adsorption Cu²⁺ of prepared material were discussed by single-actor method and the montmorillonite loaded copper ions-polyaniline was obtained. Finally an anti-corrosion coating was prepared with montmorillonite loaded copper ions-polyaniline as filler.The results showed that montmorillonite intercalated polyaniline had the best adsorption characteristics on Cu²⁺ and its light transmission rate reached 100% when the montmorillonite was 2g, the initiator (ammonium persulfate) was 0.1g, the temperature was 80°C, and the polymerization time was 2h. The prepared anti-corrosion coating had good corrosion resistance and its hardness was 90, its adhesive force reached level 1 when mass fraction of filler was 10% in total.

Abstract: Ni-B/Ni-B-B4C composite coatings on the substrate of medium-carbon steel (45#) were successfully fabricated by electroless plating in a low temperature bath. The corrosion resistance of Ni-B coating were examined by using electrochemical workstation. The results indicated that there are no pores and cracks and other defects at the interface between the substrate and composite coating. It was found that the corrosion resistance of Ni-B coating increased and then decreased with the addition of NaBH₄ increasing, and the best addition in plating bath was about 0.9 g/L. While the corrosion resistance of Ni-B coating heat-treated at 400°C with NaBH₄ addition 0.9 g/L was the worst.